▎ 摘　　要

This paper describes a detailed systematic study based on the fabrication and performance of InGaN/GaN blue light-emitting diodes (LEDs) with multilayer graphene film as a current spreading electrode. Two facile approaches to improve the electrical coupling between graphene and p-GaN layer are demonstrated. Using chemical charge transfer doping, the work function (Phi) of graphene is tuned over a wide range from 4.21 to 4.93 eV with substantial improvements in sheet resistance (R-s). Compared with pristine graphene, the chemically modified graphene on p-GaN yields several appealing characteristics such as low specific contact resistance (rho(c)) and minimized barrier height. In addition, insertion of a thin gold interlayer between graphene and p-GaN profoundly enhances the contact properties at the interface. Combining these two approaches in a single LED, the current spreading and thus the device forward voltage (V-f) are considerably improved comparable to that of an LED fabricated with an indium tin oxide electrode. The importance of pre-metal deposition oxygen plasma treatment and rapid thermal annealing in improving the contact characteristics is also addressed.